The present invention relates to an arrangement to facilitate the implantation of an electrode at an implantation site within the human body. The present invention is more particularly directed to such an arrangement for implanting an electrode of a cardiac lead within a coronary vein of the human heart.
The practice of implanting cardiac pacemakers or defibrillators in the body of a human patient generally includes the implantation of one or more electrodes in, on, or near the heart. Such electrodes are used to either sense heart activity or deliver pacing or cardioverting electrical energy to the heart. Often, an electrode may be utilized for both functions.
Pacemakers and defibrillators generally include electrical components including sense amplifiers, a pulse generator, and a battery which are housed within a sealed enclosure. The enclosures are generally implanted in a subcutaneous pocket usually located in the subclavicular region in adults or in the abdominal region in children.
The pacemakers or defibrillators are generally coupled to the heart through one or more leads which include the aforementioned electrodes. The leads include a proximal end having a connector which connects to a terminal of the pacer or defibrillator enclosure and a distal end which carries the electrode. Some leads may include more than one electrode. The body of a lead is generally composed of conductive wires surrounded by insulation. The conductive wires couple the lead connector to the lead electrode or electrodes.
An endocardial lead is a lead which is implanted within a chamber of the heart so that the distal electrode of the lead can be fixed to the inner wall of a heart chamber. In implanting such a lead, a transvenous approach is utilized wherein the lead is inserted into and passed through the subclavian, jugular, or cephalic vein and into the appropriate heart chamber. An intravenous lead is a lead which is implanted within a coronary vein such as the great vein. As disclosed in copending application Ser. No. 07/856,514, filed on Mar. 24, 1992, in the names of John M. Adams, Clifton A. Alferness, and Paul E. Kreyenhagen, and entitled IMPROVED ATRIAL DEFIBRILLATOR, LEAD SYSTEMS, AND METHOD, which application is assigned to the assignee of the present invention and incorporated herein by reference, such an intravenous lead is particularly useful in an implantable atrial defibrillator application. The distal end of the intravenous lead there disclosed is passed through the superior vena cava, the right atrium, the valve of the coronary sinus, the coronary sinus, and into a coronary vein communicating with the coronary sinus, such as the great vein. The intravenous lead includes a distal or tip electrode which, when residing in the aforementioned coronary vein, such as the great vein, is closely adjacent the left ventricle of the heart for sensing ventricular activity of the heart. The lead further includes an elongated proximal electrode which is spaced from the distal or tip electrode so that when the tip electrode is within the coronary vein, the proximal electrode resides in the coronary sinus above the left ventricle and closely adjacent the left atrium of the heart. The proximal electrode is utilized for both sensing atrial activity of the heart and delivering cardioverting electrical energy to the atria between the coronary sinus and another electrode within the right atrium which is carried by either the same aforementioned intravenous lead or by another lead.
Experience has shown that it is often difficult to feed an endocardial or intravenous lead along a desired predetermined path to implant the electrode or electrodes at a desired implantation site either in a chamber of the heart or in a desired vein near the heart. This is especially true for intravenous leads due to anomalies in vascular anatomy and the number of veins which may communicate with the desired feed path.
One arrangement in attempting to solve this problem is described in Osypka, U.S. Pat. No. 5,003,990. The arrangement there disclosed includes a guide wire which is fed along a desired path through an artery or vein and a carriage arranged to releasably receive the distal end of a lead or catheter and to be pushed along the guide wire for guiding the lead along the guide wire. When the lead or catheter reaches the desired position, the carriage must be removed from the lead or catheter and then retracted along the guide wire by the pulling of another wire attached to the carriage or by the retraction of the guide wire. Such retraction of the carriage presents the possibility of damage to an artery or vein by the carriage. In addition, releasing the carriage from the guide wire requires the lead or catheter to be bent in the area of the carriage presenting further possibilities of tissue damage during such carriage removal. Still further, once the lead or catheter is free of the carriage, its distal end will not be at its desired final implantation position. Still further, use of the carriage during both implantation of the lead or catheter and retraction of the carriage requires numerous manipulations by the physician which only adds further complexity to an already complex procedure.